Joints
Atlantoaxial joint (art. atlantoaxialis)
The connection between C1 and C2, made of three sub-joints around the dens. This is the rotation joint of the neck: roughly half of all cervical rotation happens here, the atlas turning like a ring around the peg.
- Joint type
- Compound: a median pivot joint (art. trochoidea) plus two lateral plane joints
- Body region
- Spine
- Latin name
- Articulatio atlantoaxialis
Movements, axes and normal values
| Movement | Plane | Axis | Normal range | End feel |
|---|---|---|---|---|
| Rotation | transverse | longitudinal | 40-45 degrees to each side, about half of total cervical rotation | firm springy (ligament) |
| Flexion | sagittal | transverse (mediolateral) | 10-15 degrees, considerably less than the rotation | firm springy (ligament) |
- Close-packed position
- Maximal rotation
- Resting (loose-packed) position
- Neutral head position
- Capsular pattern
- Rotation limited markedly more than all other directions.
- Arthrokinematics
- The atlas turns about the dens and drops a few millimetres in doing so, because the lateral joint surfaces are convex on convex. The transverse ligament holds the dens against the anterior arch; the alar ligaments limit rotation to the opposite side.
- Stability
- Almost entirely ligamentous: the transverse ligament as part of the cruciform ligament, the alar ligaments, the apical ligament of the dens and the tectorial membrane. Bony stability is minimal.
- Palpation
- The transverse process of the atlas lies between the mastoid process and the angle of the jaw; the spinous process of C2 is the first clearly palpable spine below the occiput. Test rotation with the head in full flexion, which locks the lower levels.
- Clinical
- Instability here is a red flag: in rheumatoid arthritis, Down syndrome and after high-energy trauma the transverse ligament can fail, after which the dens threatens the spinal cord. Dizziness, four-limb symptoms, a feeling of an unstable head or pain on lifting it are reasons not to manipulate and to refer.
- Source
- Speciële anatomie van het houdings- en bewegingsapparaat (HU, 2013); BOKS anatomie MSA (HU, 2024)